Add Unity AI Assistant package + editor settings migration

Adds com.unity.ai.assistant 2.12.0-pre.2 (+ transitive com.unity.ai.inference 2.6.1 and the com.unity.dt.app-ui EditorBuildSettings config) to the package manifest/lockfile, plus the package's ProjectSettings/Packages/com.unity.ai.assistant/Settings.json. ProjectSettings.asset migrated serializedVersion 28->29 (new iOS thermal-FPS / Android system-bar fields) by the editor. Editor/package tooling only; committed separately from the class-switch dev tool to keep concerns isolated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Packages/packages-lock.json

@@ -39,6 +39,39 @@
       "source": "embedded",
       "dependencies": {}
     },
+    "com.unity.2d.sprite": {
+      "version": "1.0.0",
+      "depth": 1,
+      "source": "builtin",
+      "dependencies": {}
+    },
+    "com.unity.ai.assistant": {
+      "version": "2.12.0-pre.2",
+      "depth": 0,
+      "source": "registry",
+      "dependencies": {
+        "com.unity.2d.sprite": "1.0.0",
+        "com.unity.mathematics": "1.3.2",
+        "com.unity.nuget.mono-cecil": "1.11.5",
+        "com.unity.modules.uielements": "1.0.0",
+        "com.unity.nuget.newtonsoft-json": "3.2.1",
+        "com.unity.modules.unitywebrequest": "1.0.0"
+      },
+      "url": "https://packages.unity.com"
+    },
+    "com.unity.ai.inference": {
+      "version": "2.6.1",
+      "depth": 0,
+      "source": "registry",
+      "dependencies": {
+        "com.unity.burst": "1.8.17",
+        "com.unity.dt.app-ui": "1.3.6",
+        "com.unity.collections": "2.4.3",
+        "com.unity.nuget.newtonsoft-json": "3.2.1",
+        "com.unity.modules.imageconversion": "1.0.0"
+      },
+      "url": "https://packages.unity.com"
+    },
     "com.unity.ai.navigation": {
       "version": "2.0.13",
       "depth": 0,
@@ -98,6 +131,18 @@
         "com.unity.test-framework.performance": "3.2.0"
       }
     },
+    "com.unity.dt.app-ui": {
+      "version": "2.1.7",
+      "depth": 1,
+      "source": "registry",
+      "dependencies": {
+        "com.unity.modules.physics": "1.0.0",
+        "com.unity.modules.androidjni": "1.0.0",
+        "com.unity.modules.uielements": "1.0.0",
+        "com.unity.modules.screencapture": "1.0.0"
+      },
+      "url": "https://packages.unity.com"
+    },
     "com.unity.entities": {
       "version": "6.5.0",
       "depth": 0,